FRESNO (AP) — The two candidates for U.S. Senate staked out conflicting positions on the nation’s immigration policy Wednesday as they rallied voters in the Central Valley, which depends heavily on immigrant labor to bring in much of California’s annual harvest.

Republican challenger Carly Fiorina blamed Democratic Sen. Barbara Boxer for casting the deciding vote to defeat a guest-worker program in Congress three years ago. Fiorina, the former CEO of Hewlett-Packard Co., said the nation needs a better guest-worker system to help farmers fill jobs in places like the Central Valley.

“When she cast that vote, she said that immigrants were a source of cheap labor that threatened the American worker. Barbara Boxer has been no friend of Fresno,” Fiorina said during a campaign stop in the farm-oriented community 175 miles south of Sacramento. “She has been no friend of the Hispanic community, and she has been no friend of the people of California.”

Boxer blamed Republicans in Congress for blocking comprehensive reform, even though changes were backed by former Republican President George W. Bush. She said she will work to enact a program in which illegal immigrants eventually could become U.S. citizens if she is elected to a fourth term.

“I’m fighting for comprehensive immigration reform,” Boxer said after a campaign rally at an active retirement community in Lincoln, 30 miles northeast of the state capital. “Of course we need border security, but we also need to make sure we have a plan so that people who work hard here … have a pathway to legality. And it would really boost our economy.”

Boxer noted that she is well ahead among Hispanic voters in polls conducted last month. That is evidence, she said, that Hispanic voters know she is fighting for their welfare.

The Field Poll found 48 percent of likely Hispanic voters favored Boxer, compared with 29 percent for Fiorina. About a quarter are undecided. A survey by the Public Policy Institute of California found Boxer with 49 percent support among likely Latino voters, compared with 19 percent for Fiorina and about one in five undecided.

Assemblyman Juan Arambula, a Democrat turned independent, said Boxer opponents are falsely trying to portray the incumbent as opposing immigration reform. He joined other Latino leaders from the Fresno area in calling on Fiorina to denounce a Spanish-language ad produced by the Latino Partnership, part of the conservative American Principles Project by Grover Norquist.

“It is an attempt to confuse Latino voters by taking one vote out of context,” Arambula said.

The lawmaker, who is termed out of office at year’s end, said Fiorina supported Arizona’s strict immigration law and does not favor a path for illegal immigrants to gain citizenship.

The ad has run recently on Spanish-language television stations in San Diego, Los Angeles and Fresno. It notes, accurately, that Boxer supports abortion rights and same-sex marriages. It also says Boxer “voted against immigration reform,” based on Boxer’s 2007 vote against a guest worker program that was to be part of a more comprehensive immigration bill.

PolitiFact, which checks the accuracy of political advertisements, has described the ad as “highly misleading” because Boxer was voting on a provision in the bill, not the bill itself. Also, the ad ignores that Boxer voted for a comprehensive immigration overhaul the year before.

The 30-second spot entitled “Our Values” is funded by two groups, the National Organization for Marriage, which opposes gay marriage, and the Susan B. Anthony List Inc., which opposes abortion. The groups spent about $200,000 on the ad.

Fiorina said Wednesday she was unfamiliar with the ad and those behind it, and said her campaign is not behind the ad. But she defended a claim that Boxer killed a guest worker program that she said was “at the heart of comprehensive immigration reform.”

Boxer said she hopes opponents can soon come together over the immigration issue.

“I believe after this election is over, people might calm down. Hopefully we’ll get it done,” Boxer told reporters.

Both candidates are courting voters in the Central Valley, which is considered key to deciding who wins the tight contest.

Fiorina needs to motivate her supporters there to have a shot at winning. Democrats could still win without strong Central Valley support as long as they turn out supporters in heavily populated coastal cities.

“We fight for every vote,” Boxer said. “We’re not taking anything for granted.”